The mobile PINE cloud simulation chamber, described in full by , was designed to reproduce the conditions of an ascending air parcel cooling adiabatically. This is achieved through expansion cooling of a chamber using a mechanical pump thus reducing pressure, reducing temperature, and increasing relative humidity. The temperature of the walls of the chamber is controlled by a cooling system that is used to set the starting temperature of the chamber walls and thus the air temperature within the chamber (to a minimum of about 213 K) prior to expansion. Each PINE run includes three stages or modes: flush, expansion, and refill. In the flush mode, ambient air is drawn through the vessel at a flow rate around 2 L min⁻¹. In the expansion mode, the inlet valve to the chamber is closed, whilst the outlet flow of air exiting the chamber is pumped at a rate of 3 to 4 L min⁻¹, causing the air within the chamber to expand. Note that all flows and concentrations reported are at standard temperature and pressure. The expansion flow acts to reduce the temperature inside the chamber and increase relative humidity and continues to a predefined minimum pressure. The instrument is capable of reproducing conditions appropriate for homogeneous freezing and heterogeneous freezing through immersion, pore-condensation, and deposition modes. In this dataset, we focus on freezing via the immersion mode, which is the dominant pathway for primary ice production in mixed-phase clouds . The humidity of the air being drawn into the chamber is controlled by two Nafion membrane diffusion dryers in parallel, which are set to keep the relative humidity high enough for cloud droplet formation to occur and low enough to avoid frost formation on the chamber walls. If excessive frost does form on the chamber walls, frost particles can become dislodged and counted as ice crystals by the optical particle counter (OPC). Regular zero checks are performed where HEPA filtered air is passed through the chamber (see , for details); the buildup of ice on the chamber walls is also avoided by regularly warming the chamber to remove any ice. The frequency with which the chamber is warmed varies between campaigns, depending on factors such as the humidity of ambient air and the flow rate through the dryers. Aerosols in the chamber can activate to cloud droplets once water saturation is exceeded, after which the droplets may freeze heterogeneously upon INPs present in the chamber. The hydrometeor size distribution (both liquid and ice) is measured with an OPC positioned downstream of the chamber in the pump line establishing the expansion flow; interstitial aerosols are too small to be counted as ice crystals. The PINE-01-A instrument uses a Palas GmbH welas 2500 OPC sensor, whilst all other instruments use a Palas GmbH fidas-pine OPC (see Table for a list of instruments used in each campaign). Ice crystals are optically larger than cloud droplets and are distinguished using a size threshold that is determined by post-processing software (see Sect. ). In the refill mode, the chamber is re-pressurized to the starting pressure at a controlled rate. The total time for each run is around 5 to 15 min and primarily determined by the time for the flush mode. The cumulative number of ice crystals (nice) measured by the OPC in the course of the expansion is used to calculate the cumulative concentration of INPs (NINP) per liter of sampled air by dividing nice by the total volume of air passing through the OPC detection volume. For the welas sensor (on PINE-01-A), this volume is 10 % of the total volume passing the OPC, whilst for the fidas-pine sensor (on all other PINEs), this volume is equal to the total volume passing the OPC. For additional details on the design and operating procedure of PINE see and ; typical output for a PINE expansion can be seen in Fig. 3.

The temperature dependence of NINP is measured by changing the wall temperature of PINE, controlled by the cooling system. In this study, typical temperature scans are performed between 240 and 263 K. Post-processing software is used to extract NINP and associated temperatures during each run and is discussed further in Sect. . estimate a temperature uncertainty of ±1 K, primarily due to the inhomogeneous temperature distribution within the chamber. The uncertainty in nice is dependent on the OPC. For the PINE-01-A instrument using the welas OPC, estimate a conservative value of ±20 %; for all other instruments that use the fidas-pine OPC, estimate a conservative value of ±10 %. In our dataset, we use counting statistics that can be used to flag the most uncertain data; this is discussed further in Sect. . assessed the aerosol loss rate between air inlet and introduction to the PINE chamber and reported a loss of less than 20 % of particles with diameter D<2 µm and about 50 % for D=4 µm. and also evaluated the loss rate in PINE during two field campaigns and report losses of 50 % at D=9.4 µm and D=8.0 µm. Fig. 24 assessed the transmission efficiency of size-resolved ambient air samples during the HyICE-2018 campaign and reports a drop in efficiency for D>5 µm. This upper size limit will not greatly affect the measured NINP but will have implications for reproducing the INP measurements from modelling studies. Following , we recommend that the upper size limit of D=5 µm is applied to simulated aerosol size distributions when comparing to the measured NINP. We plan to assess the impact of this upper limit on modelled NINP in a follow-up study.

In this dataset, we collate NINP measurements made with PINE instruments from 20 campaigns that took place between 2018 and 2024. The locations and durations of the campaigns are shown in Fig. and details of the campaigns and instruments are presented in Table . The campaigns include locations in the Arctic, Europe, North America, the North Atlantic Ocean, and East Asia. These locations are influenced by a range of important INP sources including arid environments (Central Africa, the Middle East, and Central Asia), marine environments, remote regions (the Arctic), and biologically rich environments (Europe and North America). The collated datasets provide NINP on monthly, seasonal, and annual timescales. The shortest campaign duration is 16 d, the longest is 804 d, and the mean is 172 d. A brief characterization of each campaign is provided below and includes the mean volume sampled per expansion during each campaign. The volume sampled is calculated as the inverse of the minimum measurable value of NINP (per liter of sampled air per expansion) during the campaign, which is consistent with a measurement of one ice crystal (per expansion); see Sect. for more details.

HyICE-2018: INP measurements were conducted at the SMEAR II (Station for Measuring Ecosystem-Atmosphere Relations) station located in the boreal forest in Hyytiälä, Finland. Aerosols were sampled through a heated total aerosol inlet 6 m above ground level. PINE was set to the following operation parameters: (1) Flush at 3 L min⁻¹ for 4 min, (2) expansion at 4 L min⁻¹ to 700 mbar, (3) refill at 3 L min⁻¹. The mean volume of air sampled during a single expansion was ∼2.0×10-3 m³. More details on the campaign can be found in and .

PICNIC: INP measurements were conducted at the Site d’Observations Atmosphériques Puy de Dôme, a mountain-top site in France. It is an observational facility of the ACTRIS (Aerosol, Clouds, and Trace Gases Research Infrastructure) and the Global Atmosphere Watch (GAW) measurement programs. Sampling was performed via a heated whole-air inlet situated 2 m above the laboratory roof. PINE measurements were conducted with the following program: (1) Flush for 5 min at 2 L min⁻¹, (2) expansion at 3 L min⁻¹ to 650 mbar (ambient pressure 850 mbar), (3) refill at 2 L min⁻¹. The mean volume of air sampled during a single expansion was ∼1.5×10-3 m³. More details on the campaign can be found in .

ExINP-SGP: PINE measurements were made at the US Department of Energy (DOE) Southern Great Plains (SGP) Atmospheric Radiation Measurement (ARM) site in Oklahoma, US. The site is surrounded by farmland. The PINE instrument was housed within the Guest User Facility, with ambient air sampled through a 0.15 m diameter quasi-laminar sampling inlet with a total suspended particulate (TSP) sampling head at 5.5 m above the ground. The measurement program was the following: (1) Flush for 5 min at 2 L min⁻¹, (2) expansion at 3 L min⁻¹ to 750 mbar, (3) refill at 2 L min⁻¹ to ambient pressure. The mean volume of air sampled during a single expansion was ∼4.0×10-3 m³. More details on this campaign can be found in .

ExINP-ENA: PINE measurements were made at the US DOE Eastern North Atlantic (ENA) ARM site on Graciosa Island, Azores. The PINE instrument was housed in an air-conditioned container on the site, with ambient air sampled through a 0.1 m diameter quasi-laminar sampling inlet with a TSP sampling head at 5.5 m above the ground. The measurement program was the following: (1) Flush for 10 min at 2 L min⁻¹, (2) expansion at 3 L min⁻¹ to 800 mbar, (3) refill at 2 L min⁻¹ to ambient pressure. The mean volume of air sampled during a single expansion was ∼2.8×10-3 m³. More details on this campaign can be found in .

CORONA-PINE04 and CORONA-PINE01: The CORONA campaign was conducted at the AIDA (Aerosol Interaction and Dynamics in the Atmosphere) facility at the Karlsruhe Institute of Technology (KIT), Campus North in Germany. PINE was installed at a PM₁₀ non-heated aerosol inlet, as icing during winter was not expected. The inlet was installed 1 m above the laboratory roof and 9 m above ground. INP measurements were alternately conducted with the PINE models PINE-01-A and PINE-04-01. The measurement program was the following: (1) Flush for 3 min (PINE-01-A) or 4 min (PINE-04-01) at 2 L min⁻¹, (2) expansion at 3 L min⁻¹ to 820 mbar, (3) refill at 2 L min⁻¹. The mean volume of air sampled during a single expansion was ∼1.5×10-3 m³ (PINE-1A) or ∼2.3×10-3 m³ (PINE-04); the different volumes sampled per expansion reflect chamber volume in each instrument (7×10-3 m³ for PINE-01-A and 10×10-3 m³ for PINE-04-01). The datasets are published , but no accompanying papers are currently available.

CountIce-pt1 and CountIce-pt2: PINE measurements were made within the Leeds IcePod mobile laboratory located on the University of Leeds campus, UK. The site was characterized as an urban environment with low-rise buildings. Ambient air was sampled through a heated TSP sampling head (DTSP03/00/16, Digitel, Switzerland) on a 2 m sampling tube. A flow splitter was used to direct part of the air flow into PINE. Each expansion was operated with the following program: (1) Flush for 5 min at 2 L min⁻¹, (2) expansion at 3 L min⁻¹ down to 840 mbar, (3) refill at 2 L min⁻¹. A year gap between the two campaigns occurred due to the deployment of the PINE instrument on the M-Phase campaign. The mean volume of air sampled during a single expansion was ∼2.0×10-3 m³ for both campaign periods. The datasets are published , but no accompanying papers are currently available.

SBO21: PINE measurements were made at the Sonnblick Observatory (SBO), which is located in Austria on the summit of the mount “Hoher Sonnblick”. Ambient air was sampled through a heated total aerosol inlet designed according to GAW guidelines, with an upper cut-off size of 20 µm at a wind speed of 20 m s⁻¹. The inlet was located at the rooftop of the station. Each expansion in PINE was operated with the following program: (1) Flush for 4 min at 1.5 L min⁻¹, (2) expansion at 3 L min⁻¹ down to 575–600 mbar, (3) refill at 1.5 L min⁻¹. The mean volume of air sampled during a single expansion was ∼1.4×10-3 m³. More information can be found in .

SPL01: PINE measured INP concentrations at Storm Peak Laboratory, a mountain-top site in the Rocky Mountains , US. The site is operated by the University of Utah and supported by the National Science Foundation (NSF). The instrument was connected to one of the facility’s heated inlets, with the following measurement program: (1) Flush for 5 min at 1 L min⁻¹, (2) expansion at 3 L min⁻¹ to 530 mbar (ambient pressure 685 mbar), (3) refill at 1 L min⁻¹. The mean volume of air sampled during a single expansion was ∼1.4×10-3 m³. The dataset is published , but no accompanying paper is currently available.

CALISHTO: INP measurements were performed at the (HAC)² (Helmos Hellenic Atmospheric Aerosol and Climate Change) station at the top of Mount Helmos, Greece. Sampling was performed through an omnidirectional total inlet installed on the rooftop of the observatory. PINE was operated with the following program: (1) Flush for 5 min at 1 L min⁻¹, (2) expansion at 3 L min⁻¹ to 650 mbar, (3) refill at 1 L min⁻¹. The mean volume of air sampled during a single expansion was ∼1.5×10-3 m³. Information on the measurement campaign can be found in .

ExINP-NSA: PINE measurements were made at the Barrow Atmospheric Baseline Observatory, next to the US DOE North Slope of Alaska (NSA) ARM site, located close to the town of Utqiaġvik, Alaska. The PINE instrument was located inside the observatory and sampled ambient air through stainless steel sampling pickup inlets (19 mm diameter) connected to a polyvinyl chloride vertical sampling stack (0.1 m diameter) 12 m above the ground. A 9.5 mm conductive tube bridged the pickup port to the instruments in the observatory. The measurement program was the following: (1) Flush for 10 min at 2 L min⁻¹, (2) expansion at 3 L min⁻¹ to 800 mbar, (3) refill at 2 L min⁻¹ to ambient pressure. The mean volume of air sampled during a single expansion was ∼3.0×10-3 m³. More information can be found in .

BEIJING. INP measurements were made at the Beijing Cloud Laboratory and Observational Utilities Deployment Base (CLOUD Base, CB). The site is located in Pinggu District, Beijing, China, and is situated on a plain surrounded by farmland and low-rise buildings. The instrument was installed at a PM₁ non-heated aerosol inlet as icing was not expected during winter. The inlet was installed 1 m above the laboratory roof and 12 m above ground. The measurement program was the following: (1) Flush for 3 min at 1.5 L min⁻¹, (2) expansion at 3 L min⁻¹ to 850 mbar, (3) refill at 1.5 L min⁻¹. Note that measurements below the lower limit of measurable concentration (see Sect. ) were not included in the Level 1 data for this campaign; therefore, we omit all data above a temperature threshold of 252.15 K. This removes expansions within a temperature regime where we would expect to encounter low concentrations with poor counting statistics (see Fig. ). The mean volume of air sampled during a single expansion was ∼2.4×10-3 m³. The dataset is published , but no accompanying paper is currently available.

M-Phase: PINE measurements were made within the Leeds IcePod mobile laboratory onboard the RRS Discovery during the joint M-Phase/SEANA research cruise in the Labrador Sea. The IcePod was located on the foredeck, forward of the ship stack. Ambient air was sampled through a heated TSP sampling head (DTSP03/00/16, Digitel, Switzerland) on a 2 m sampling tube. A flow splitter was used to direct part of the air flow into PINE. Each expansion was operated with the following program: (1) Flush for 5 min at 2 L min⁻¹, (2) expansion at 3 L min⁻¹ down to 840 mbar, (3) refill at 2 L min⁻¹. The mean volume of air sampled during a single expansion was ∼2.2×10-3 m³. The dataset is published , but no accompanying paper is currently available.

PaCE22: PINE measurements were conducted at the Pallas Sammaltunturi station in northern Finland around 170 km north of the Arctic Circle, representing sub-Arctic conditions. The site is within the Pallas-Yllästunturi National Park on top of a hill above the boreal forest tree line. PINE was connected to the heated whole air inlet of the station. Each expansion was operated with the following program: (1) Flush for 4 min at 1 L min⁻¹, (2) expansion at 3 L min⁻¹ from around 950 to 800 mbar, (3) refill at 1 L min⁻¹. The mean volume of air sampled during a single expansion was ∼1.8×10-3 m³. An overview of the PaCE22 (Pallas Cloud Experiment 2022) campaign can be found in , , and , whilst more information on the PINE measurements can be found in .

PUY: PINE measurements were made at the Puy de Dôme station, located at the highest point of the Chaîne des Puys, a volcanic mountain range in central France. PINE was connected to the whole air inlet of the station (50 % loss of particles at 30 µm). Ambient aerosol particles sampled through the inlet are passively dried to approximately 40 % relative humidity with respect to water (RHw) before being sampled by the instrument. Each expansion was operated with the following program: (1) Flush for 7.5 min at 2 L min⁻¹, (2) expansion at 3 L min⁻¹ from around 850 to 700 mbar, (3) refill at 2 L min⁻¹. The mean volume of air sampled during a single expansion was ∼1.9×10-3 m³. More information on this campaign can be found in .

ExINP-GVB: INP concentration measurements during this campaign were performed at Gruvebadet Atmosphere Laboratory in the high Arctic, in close proximity of the Ny-Alesund Research Station on Svalbard. PINE was attached to the heated whole air inlet and the following measurement program was used: (1) Flush for 5 min at 2 L min⁻¹, (2) expansion at 3 L min⁻¹ from around 1000 to 850 mbar, (3) refill at 2 L min⁻¹. The mean volume of air sampled during a single expansion was ∼2.4×10-3 m³. The dataset is published , but no accompanying paper is currently available.

LIFE-FROSTDEFEND: INP measurements during the LIFE-FROSTDEFEND campaign were conducted in a mobile container, placed in a lemon orchard near Aigio, Greece. Aerosol sampling was performed via a PM₁₀ inlet, about 1 m above the container roof. PINE was operated with the following program: (1) Flush for 4 min a 1 L min⁻¹, (2) expansion with 3 L min⁻¹ to 880 mbar, (3) refill at 1 L min⁻¹. The mean volume of air sampled during a single expansion was ∼1.8×10-3 m³. The dataset is published , but no accompanying paper is currently available.

ExINP-ZEP: PINE measurements were performed at the Zeppelin observatory at Mt. Zeppelin , located in the high Arctic on Svalbard. The station is located south of Ny-Alesund Research Station, however, due to frequent temperature inversions the site is typically shielded from anthropogenic emission from the village. PINE was connected to a ground-based counterflow virtual impactor for measurements of cloud residuals, and a heated whole air inlet (see , for more details). In this study we only present measurements from the whole air inlet. The following program was used: (1) Flush for 5 min at 2 L min⁻¹, (2) expansion at 3 L min⁻¹ from around 930 to 790 mbar, (3) refill at 2 L min⁻¹. The mean volume of air sampled during a single expansion was ∼2.1×10-3 m³. The dataset is published , but no accompanying paper is currently available.

WAO: PINE measurements were made within the Leeds IcePod mobile laboratory located at the Weybourne Atmospheric Observatory (WAO), a GAW Regional station on the Norfolk coast of the UK. Ambient air was sampled through a heated TSP sampling head (DTSP03/00/16, Digitel, Switzerland) on a 2 m sampling tube. A flow splitter was used to direct part of the air flow into PINE. Each expansion was operated with the following program: (1) Flush for 5 min at 2 L min⁻¹, (2) expansion at 3 L min⁻¹ down to 840 mbar, (3) refill at 2 L min⁻¹. The mean volume of air sampled during a single expansion was ∼2.5×10-3 m³. The dataset is published , but no accompanying paper is currently available.

Post-processing software is used to convert the raw Level 0 data from each PINE run into relevant Level 1 data; a full description and evaluation can be found in . The key information taken from the Level 0 data includes the minimum temperature during the expansion and the hydrometeor size distribution measured by the OPC between the start and end of the expansion, which the software uses to establish a size threshold for each expansion. This threshold, typically on the order of 10 µm , is used to separate the smaller liquid droplets from the larger ice particles, thus determining nice; NINP can then be calculated following the process described in Sect. . The key Level 1 variables that are relevant for this dataset are the expansion time (UTC), the minimum temperature (Tmin), and the number concentration of activated INPs per liter of sampled air under standard conditions (273.15 K and 1013.25 hPa). Seventeen of the campaign datasets (Table ) use the publicly available PINE INP Analysis software PIA, described by and developed at KIT, and three use a variation developed by WTAMU, which differs in how the size threshold is determined. In the PIA software, the threshold is determined for each PINE expansion (see , for an evaluation of this method), and in the WTAMU software, a single threshold is determined over an “operation period” which may include anywhere between one run and more than 100 runs Sect. S8. Both software packages include automatic quality control to flag the data, which is used by each campaign team to remove poor quality data. A comparison of the two methods for the ExINP-ENA Level 1 data yields an r-squared value of 0.97, demonstrating good consistency between the methods. For some campaigns, upper or lower temperature ranges were used to manually flag data from temperature regimes that are deemed uncertain. In this dataset, we have removed all Level 1 flagged data.

The GloPINE dataset is provided as individual NetCDF4 (.nc) files corresponding to each campaign. This permits the addition of further campaigns in the future. The file attributes are the campaign name, the PINE instrument used to make the measurements, and the duration of the campaign. Each variable is suffixed with “6h” or “6h2K” to denote the subsetting interval in time or time/temperature. The variables included in each file are:

latitude_6h: mean latitude(s) of campaign (° N)

Note that concentrations of NINP(T,t) are converted from units of L⁻¹ and provided in SI units of m⁻³. Missing values are set to a value of -999 and represent binning intervals that did not include any PINE expansions. Values of zero in the variables INP_6h2K and RSD_6h2K represent intervals when at least one PINE expansion was performed but the sum of measured ice crystals was zero; we keep these in for consistency with the Level 1 datasets. All campaigns have geospatial variables (latitude_6h, longitude_6h, and altitude_6h) in dimensions of time. This permits a consistent format for campaigns that were either in a fixed location (e.g., ExINP-NSA) or a variable location (e.g., the M-Phase cruise campaign). For campaigns in a fixed location, the values are constant throughout the timeseries. For application of the GloPINE dataset with simulated data or reanalysis products, we recommend that the user collocates their data with the latitude, longitude, time, and altitude of each individual GloPINE data point. When calculating INP concentrations, we recommend applying the interval-mean temperature and, for consistency with the measurement technique, only using the portion of the aerosol size distribution below D=5 µm (see Sect. ).